Modulating butterfly valve control

Abstract

A method and system for controlling a fluid valve are described that avoid the effects of hysteresis. In hysteresis, the power signals associated with a valve position are different on the upstroke and downstroke. As a result, predicting the valve position can be difficult if you only know the current power signal. Instead of using upstrokes and downstrokes, a valve can momentarily be set to zero power, or a rest position when receiving a new command signal. This way the command signal is applied from a zero power or rest position, making the valve position more predictable and accurate.

What is claimed is: 
     
       1. A butterfly valve for manipulating fluid flow, comprising:
 a housing configured to receive a fluid; 
 a disc configured to rotate on its axis within the housing; and 
 a controller configured to regulate fluid flow through the butterfly valve by rotating the disc on its axis, wherein the controller is configured to apply a first input signal to move the disc from a rest position to a first position located a first rotational distance from the rest position, and wherein when the controller receives a command to move the disc to a second position located a second rotational distance from the rest position, if the second rotational distance is larger than the first rotational distance, then the controller applies a second input signal associated with the second position, and if the second rotational distance is smaller than the first rotational distance, then the controller momentarily applies an input associated with the rest position and then applies the second input signal associated with the second position. 
 
     
     
       2. The butterfly valve of  claim 1  wherein the rest position comprises a closed position. 
     
     
       3. The butterfly valve of  claim 1  wherein the rest position comprises an open position. 
     
     
       4. The butterfly valve of  claim 1  wherein the controller comprises a computer remote to the disc. 
     
     
       5. The butterfly valve of  claim 1  wherein the controller is communicatively coupled to a remote computer. 
     
     
       6. The butterfly valve of  claim 1  wherein the controller is communicatively coupled to a vehicle control system. 
     
     
       7. The butterfly valve of  claim 1  wherein the butterfly valve is operable to regulate a flow of air in a helicopter. 
     
     
       8. The butterfly valve of  claim 1  wherein the controller is communicatively coupled to a control system for an aircraft. 
     
     
       9. A valve for controlling fluid flow, comprising:
 a housing configured to receive a fluid; 
 a barrier operable to at least partially restrict a flow of the fluid through the housing; and 
 a controller configured to adjust the barrier, wherein the controller is configured to receive a first command to apply a first input signal to the barrier, the first input signal associated with moving the barrier from a rest position to a first position, the controller further configured to receive a second command to apply a second input signal to the barrier, the second input signal associated with moving the barrier from the rest position to a second position, wherein if the second position is between the rest position and the first position, then the controller is configured to adjust the barrier to the rest position momentarily and then to apply the second input signal. 
 
     
     
       10. The valve of  claim 9  wherein the valve comprises a gate valve and the barrier comprises a gate. 
     
     
       11. The valve of  claim 9  wherein the housing comprises a plastic. 
     
     
       12. The valve of  claim 9  wherein the valve comprises an air flow system in an aircraft. 
     
     
       13. The valve of  claim 9  wherein the controller is communicatively coupled to a control system of an aircraft. 
     
     
       14. The valve of  claim 9  wherein the controller is communicatively coupled to an HVAC control system. 
     
     
       15. The valve of  claim 9  wherein the controller is coupled to the gate by an actuator. 
     
     
       16. The valve of  claim 9  wherein the rest position is associated with an input signal of 0. 
     
     
       17. A method of controlling a fluid valve, comprising:
 sending a first command signal to a controller for the fluid valve, the controller configured to adjust a barrier of the fluid valve to a first position from a rest position; and 
 sending a second command signal to the controller, the second command signal associated with a second position between the first position and the rest position, wherein the controller is configured to, upon receiving the second command signal, adjust the barrier to the rest position momentarily and then adjust the barrier to the second position. 
 
     
     
       18. The method of  claim 17 , wherein the rest position is an open position. 
     
     
       19. The method of  claim 17 , wherein the rest position is a closed position. 
     
     
       20. The method of  claim 17 , wherein the fluid valve comprises a ball valve.